Transmission Of Electromagnetic Waves Research Articles

Microwave birefringent metamaterials for polarization conversion based on spoof surface plasmon polariton modes.

We propose the design of wideband birefringent metamaterials based on spoof surface plasmon polaritons (SSPPs). Spatial k-dispersion design of SSPP modes in metamaterials is adopted to achieve high-efficiency transmission of electromagnetic waves through the metamaterial layer. By anisotropic design, the transmission phase accumulation in metamaterials can be independently modulated for x- and y-polarized components of incident waves. Since the dispersion curve of SSPPs is nonlinear, frequency-dependent phase differences can be obtained between the two orthogonal components of transmitted waves. As an example, we demonstrate a microwave birefringent metamaterials composed of fishbone structures. The full-polarization-state conversions on the zero-longitude line of Poincaré sphere can be fulfilled twice in 6–20 GHz for both linearly polarized (LP) and circularly polarized (CP) waves incidence. Besides, at a given frequency, the full-polarization-state conversion can be achieved by changing the polarization angle of the incident LP waves. Both the simulation and experiment results verify the high-efficiency polarization conversion functions of the birefringent metamaterial, including circular-to-circular, circular-to-linear(linear-to-circular), linear-to-linear polarization conversions.

A Novel Passive Wireless Sensor for Concrete Humidity Monitoring.

This paper presents a passive wireless humidity sensor for concrete monitoring. After discussing the transmission of electromagnetic wave in concrete, a novel architecture of wireless humidity sensor, based on Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) technology, is proposed for low-power application. The humidity sensor utilizes the top metal layer to form the interdigitated electrodes, which were then filled with polyimide as the humidity sensing layer. The sensor interface converts the humidity capacitance into a digital signal in the frequency domain. A two-stage rectifier adopts a dynamic bias-voltage generator to boost the effective gate-source voltage of the switches in differential-drive architecture. The clock generator employs a novel structure to reduce the internal voltage swing. The measurement results show that our proposed wireless humidity can achieve a high linearity with a normalized sensitivity of 0.55% %RH at 20 °C. Despite the high losses of concrete, the proposed wireless humidity sensor achieves reliable communication performances in passive mode. The maximum operating distance is 0.52 m when the proposed wireless sensor is embedded into the concrete at the depth of 8 cm. The measured results are highly consistent with the results measured by traditional methods.

Pancharatnam-Berry Phase Induced Spin-Selective Transmission in Herringbone Dielectric Metamaterials.

A dielectric metamaterial approach for achieving spin-selective transmission of electromagnetic waves is proposed. The design is based on spin-controlled constructive or destructive interference between propagating phase and Pancharatnam-Berry phase. The dielectric metamaterial, consisting of monolithic silicon herringbone structures, exhibits a broadband operation in the terahertz regime.

Fission Transmission Linear-to-Circular Polarization Conversion Based on Compact Bi-Layer structure

<p>A fission transmission linear-to-circular polarization conversion based on bi-layer structure is proposed which is composed of 3 × 3 array to convert linear-to-circular polarized wave. The structure is constructed by half square with “H” shape printed on both sides of the dielectric substrate that are subjected to obtain multi-band at resonance frequencies. The proposed structure realizes the giant circular polarization under the normal incidence for right and left circular polarized waves. After transmission, the incident wave decomposed into two orthogonal linear components have equal magnitudes and 90o phase difference between them. The novel approach of “fission transmission of electromagnetic waves” is firstly introduced to understand the physics of giant circular polarization conversion which is based on the sequence of incident and transmitted waves to generate strong circular dichroism.</p>

Exploration of photonic crystal circulator based on gyromagnetic properties and scaling of ferrite materials

Three port optical circulators are designed predicated on two dimensional triangular lattice photonic crystals and examined with different size of regular (circular) and irregular (triangular) ferrite posts, through the structure optimization and exploration of defect mode coupling. Ferrite, a special type of highly permeable and low-loss magnetic material, which is anisotropic when biased by a much larger static magnetic field is modeled and the gyromagnetic property of the same is investigated. According to theoretical analysis, the optimized geometry structure can make the non-reciprocal transmission of electromagnetic waves accompanying a high caliber isolation and low insertion loss with the avail of ferrite post inserted at the center of the joint. In order to minimize the reflections in the isolated port at the nominal frequencies, the scaling of ferrite post is implemented by defining S parameter. The structural optimization and the calculation of tensor elements of the anisotropic medium is executed by the finite element method. Moreover, the further study shows the importance of scaling the magneto-photonic material and the way it affects the transmission and isolation of the structured contrivance. Numerical simulations are performed to manifest the attainability and the characteristics of the designed circulators. Finally the triangular ferrite post with the scale of 0.518 makes the non-reciprocal transmission of electromagnetic waves with the minimum insertion loss at the normalized frequency range of 191.6GHz which benefits from a broad operational bandwidth. This optimized device can realize the operations of splitting, routing and isolation and have good technological compatibility for chip level integration into Photonic Integrated Circuits.

Boron Nitride and Sapphire Windows for 95-GHz Gaussian RF Beam

This paper presents the reflectivity and insertion loss characteristics of Boron Nitride (BN) and Sapphire RF windows for a 95-GHz Gaussian RF beam of a 100-kW gyrotron. The design of an RF window has been carried out using Fresnel’s formula for reflection and transmission of Gaussian electromagnetic wave at the boundary between two media. The return loss of the RF windows of 95 GHz was found to be less than −46.8 dB for BN and less than −57.8 dB for Sapphire, and the transmission loss of the RF windows was better than −0.06 dB for BN and better than −0.01 dB for Sapphire. Furthermore, the heat load due to RF power absorption over the disk surface has been calculated. The Sapphire RF windows have been found with lower heat load and deflection, and higher tensile stress than that of BN. The allowable stress level for Sapphire is higher than that of BN; therefore, using Sapphire is structurally safer to use.

The method of impedance transformation for electromagnetic waves propagating in one-dimension plasma photonic crystal

This study focuses on the transmission of normal-incidence electromagnetic waves in one-dimensional plasma photonic crystals. Using the Maxwell's equations in a medium, a method that is based on the concept of impendence is employed to perform the simulation. The accuracy of the method was evaluated by simulating a one-layer plasma and conventional photonic crystal. In frequency-domain, the transmission and reflection coefficients in the unmagnetized plasma photonic crystal were calculated, and the influence factors on plasma photonic crystals including dielectric constants of dielectric, spatial period, filling factor, plasma frequency, and collision frequency were studied.

Transmission of terahertz waves through layered superconductors controlled by a dc magnetic field

The transmission of THz electromagnetic waves via a slab of layered superconductor in the presence of dc magnetic field ${H}_{0}$ is theoretically studied. We demonstrate that the external dc field turns the layered superconductor into nonuniform medium with spatially and frequency-dependent dielectric permittivity. Even a relatively weak dc magnetic field, when the superconductor is in the Meissner state, significantly affects the transmittance of the layered superconductor. Moreover, the proper choice of ${H}_{0}$ can provide the perfect transparency of the slab. In addition, the dc magnetic field changes the dependence of the transmittance on the slab thickness, the frequency, and the incident angle of the wave. Thus, it can serve as an effective tool to control the transmissivity of layered superconductors.

Transmission of electromagnetic waves through thin Cu films

Optical transmission is used to study the electronic structure of nanosized Cu phases that are obtained on the surface of single-crystalline NaCl (100) using vacuum deposition. It is demonstrated that Cu nanofilms with a thickness of 1–1.5 monolayers exhibit properties typical of narrow-band-gap semiconductors.

Electromagnetic wave transmission of over-dense plasma with parabolic electric permittivity profile

Electromagnetic wave transmission of over-dense plasma with parabolic electric permittivity profile

Extraordinary transmission of electromagnetic waves through sub-wavelength slot arrays mediated by spoof surface plasmon polaritons

One-dimensional gratings consisting of sub-wavelength metallic slot arrays have been widely applied in the design of novel devices due to their polarization-selective characteristics. When the incident electric field is polarized along the slot direction, the slot arrays are opaque, behaving like a metal surface. Here we propose a scheme of making slot arrays transparent for electromagnetic (EM) waves, which is achieved by the incorporation of corrugated metal strip arrays. Incident waves are first converted into spoof surface plasmon polaritons (SSPPs) propagating along the strips. Since SSPPs confine EM fields in sub-wavelength scales, EM waves can penetrate through the sub-wavelength slots. High transmission was thus obtained, with an efficiency as high as 95%. Moreover, position and bandwidth of the transmission band can be tailored by adjusting the groove depth and the slot width, respectively. It is expected that the design may find potential applications in the multifunctional devices with frequency- and polarization-selective features.

Propagation of electromagnetic waves through a multilayered structure containing diamond-like carbon, porous silicon, and left-handed material

In this work, reflection and transmission of electromagnetic wave through a multilayered structure containing diamond-like carbon, porous silicon, and left-handed material (LHM) are investigated theoretically and numerically. The mentioned materials are described, and their main parameters are given in detail. After the construction of the problem, the reflection and transmission coefficients are derived in a closed form by a transfer matrix method. The reflected and transmitted powers of the structure are calculated using these coefficients. In the numerical results, the mentioned powers are computed and illustrated as a function of frequency, angle of incidence, and slabs thickness, when the damping coefficient of the LHM changes. The results obtained may be useful to the researchers and designer working in the area solar cells.

Nonextensivity effect on radio-wave transmission in plasma sheath

In this paper, new theoretical findings on the application of magnetic field in effective transmission of electromagnetic (EM) waves through a plasma sheath around a hypersonic vehicle are reported. The results are obtained by assuming the plasma sheath to consist of nonextensive electrons and thermal ions. The expressions for the electric field and effective collision frequency are derived analytically in the framework of nonextensive statistics. Examination of the reflection, transmission, and absorption coefficients regarding the strength of the ambient magnetic field shows the significance of q-nonextensive parameter effect on these entities. For small values of the magnetic field, the transmission coefficient increases to unity only in the range of −1<q<1. It is also found that the EM wave transmission through the nonextensive plasma sheath can take place using lower magnetic field strengths in the presence of superthermal electrons compared with that of Maxwellian ones. It is observed that superthermal electrons, with nonextensive parameter, q < 1, play a dominant role in overcoming the radio blackout for hypersonic flights.

A physical explanation for the all-angle reflectionless property of transformation optics designs

In this paper, the all-angle reflectionless property of transformation optics devices is analyzed, and a physical explanation is provided for it. To this end, plane wave propagation through a planar boundary separating two homogenous, lossless magnetically anisotropic media is studied. The general form of material parameters enabling an all-angle reflectionless transmission of electromagnetic waves through the boundary is derived. Similarities are drawn between this general form of all-angle reflectionless material parameters and those observed in transformation optics designs. The findings are verified through full-wave simulation. Furthermore, a physical explanation as to why the general form of anisotropic material parameters are reflectionless for all angle of incidences is provided. This work provides an intuitive understanding of the inherent reflectionless property of transformation optics devices, and may find applications in designing reflectionless media to control electromagnetic waves without the use of coordinate transformations.

Development of hybrid composite radar wave absorbing structure for stealth applications

The ideally invisible stealth radomes are usually sandwiched constructions composed of E-glass/epoxy composite, polyvinyl chloride foam and frequency selective surfaces (FSS). Nylon 6/6 and balsa wood are well known for their low dielectric properties. In this work the electromagnetic (EM) wave transmission characteristics of the existing stealth radomes were improved by employing nylon 6/6 fibre and balsa wood, along with E-glass/epoxy composite without compromising the mechanical properties. The free space measurement technique was performed to measure the EM wave transmission characteristics in the X-band frequency range (8.2–12.4 GHz) for a specific FSS. The flexural strength of the sandwiched constructions were investigated with three-point bending test.

Transmission and Detection of Electromagnetic Waves for Gesture Recognition

Hand gesture technology makes users’ lives simpler, achieving “hands free” interaction through eliminating the need to hold or press the device. Since the need of human computer interaction has increased to a great-extent, such a technique needs to be devised that do not depend on Vision or Wearable sensors approach. This paper is a sincere attempt to recognize gestures using EM field detection approach. This requires only an EM field transmitter and a detector (receiver). The novelty of this approach is, it not only reduces extra cost for wearable or vision based sensors but would also account for a wide range of coverage area. In addition to this, method to recognize gestures through EM Waves with the help of a laser light is also practically implemented. The demonstration of this method is illustrated with the help of Macromedia Flash Player. This theory will certainly reduce the cost factor and add to the simplicity of the current human computer interactions.

Transmission of electromagnetic wave from anisotropic plasma coated nihility circular cylinder

Transmission of electromagnetic wave from anisotropic plasma coated nihility circular cylinder

A NONRECIPROCAL MULTI-CHANNEL BANDSTOP FILTER USING THE GENERALIZED FIBONACCI MULTIFERROIC SUPERLATTICES WITH THE SILVER-MEAN SEQUENCE

The generalized Fibonacci multiferroic superlattices (GFMS) are composed of single-phase multiferroic domains with simultaneous polarization and magnetization and are defined by the binary substitutional rule (B −→ BmA, A −→ B, m = 2, 3). We propose to construct a nonreciprocal multichannel bandstop filter by the GFMS. The couplings between electromagnetic waves and lattice vibration of multiferroic material with ferroelectric and ferromagnetic (or antiferromagnetic) orders can be invoked either through piezoelectric or piezomagnetic effects and can lead to the creation of polaritonic band structure. The plane wave expansion method with first-order approximation predicts the existence of multiple band gaps, and electromagnetic waves lying within the band gaps are prohibited, and the band gaps with respect to forward electromagnetic waves (FEWs) and backward electromagnetic waves (BEWs) are asymmetric. The forbidden band structures with FEWs and BEWs are calculated by the transfer matrix method and multiple frequency channels with unidirectional transmission of electromagnetic waves can be further confirmed. Nine and twenty transmission dips in transmission spectra for the BEWs in the frequency range of ω = 0.4–0.6 (17.06 GHz–25.59 GHz) are found in the GFMS with m = 2 and 3, respectively, in which the BEWs are prohibited while the FEWs can travel. Thus, the GFMS has all the conditions for the nonreciprocal multi-channel bandstop filter. Besides, the GFMS can also be applied to construct compact multi-channel one-way electromagnetic waveguides.

Multiband Circular Polarizer Based on Fission Transmission of Linearly Polarized Wave forX-Band Applications

A multiband circular polarizer based on fission transmission of linearly polarized wave forx-band application is proposed, which is constructed of 2 × 2 metallic strips array. The linear-to-circular polarization conversion is obtained by decomposing the linearly incidentx-polarized wave into two orthogonal vector components of equal amplitude and 90° phase difference between them. The innovative approach of “fission transmission of linear-to-circular polarized wave” is firstly introduced to obtain giant circular dichroism based on decomposition of orthogonal vector components through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer and two transmitted waves impinge on the upper printed strips layer to convert into four orthogonal vector components at the end of structure. This projection and transmission sequence of orthogonal components sustain the chain transmission of electromagnetic wave and can achieve giant circular dichroism. Theoretical analysis and microwave experiments are presented to validate the performance of the structure. The measured results are in good agreement with simulation results. In addition, the proposed circular polarizer exhibits the optimal performance with respect to the normal incidence. The right handed circularly polarized wave is emitted ranging from 10.08 GHz to 10.53 GHz and 10.78 GHz to 11.12 GHz, while the left handed circular polarized wave is excited at 10.54 GHz–10.70 GHz and 11.13 GHz–11.14 GHz, respectively.

Accurate Circuit Modeling of Fishnet Structures for Negative-Index-Medium Applications

Metallic plates with a two-dimensional (2D) periodic distribution of sub-wavelength apertures are known to exhibit extraordinary transmission of electromagnetic waves. Stacking two or more of such plates gives place to the so-called fishnet structures, which constitute a popular way of achieving an effective negative index medium at frequencies ranging from microwaves to optics. Unfortunately, a general wideband equivalent circuit has not yet been proposed to facilitate its understanding and design. This work presents this circuit model with closed-form expressions for the circuit elements, thus making it possible to obtain the electrical response for this class of structures in a very efficient way. This procedure is much faster than alternative numerical methods at the same time that it retains a high level of accuracy when compared with some other oversimplified models. The circuit model also provides a simple rationale as well as a good physical insight in order to explain the qualitative behavior of such structures, independently of the number of stacked layers.